1. Field of the Invention
The present invention relates to a flat display apparatus having an array of field emission cathodes (emitter electrodes).
2. Description of the Related Art
A flat display apparatus having an array of electric-field emission cathodes is known as the related art.
The flat display apparatus is comprised of a silicon substrate on which are successively deposited a silicon oxide or other insulating film and gate electrodes. In the array of cavities between the gate electrodes and the insulating film, an array of microcathodes with tapered front ends is arranged.
A counter plate on which a fluorescent screen is formed is disposed at a predetermined distance from the substrate on which the microcathodes are formed. The flat display is realized by the emission of electrons to the fluorescent screen from the front ends of the microcathodes scanned by the gate electrodes.
In the flat display apparatus of this related art, it is important that the radii of curvature of the front ends of the microcathodes be kept uniform. If there is any variation in the radii of curvature, the front ends of some of the microcathodes will be destroyed by the emission, electrons will not be emitted, and therefore there will be pixel defects.
A technique has been developed for ensuring a uniform radii of curvature for the front ends of microcathodes.
In a flat display apparatus having microcathodes of this construction however, since it is basically necessary to fabricate an array of microcathodes with tapered front ends, the process of forming of the microcathodes becomes complicated. Accordingly, the achievement of a uniform radius of curvature for the front end of each of the microcathodes and uniform arrangement at relative positions with respect to the gate electrodes (extraction voltage) remains difficult, variations occur in the extraction voltage, and the problem of a shortened useful life due to the destruction of the front ends of the microcathodes remains.